The invention is based on a circuit module and on a method for producing such a circuit module.
Controllers are known generally for controlling a wide variety of functions and devices and are increasingly being used in the automotive sector for the purpose of controlling a wide variety of functions of a motor vehicle. The rapidly rising number of electrical and electronic applications in modern motor vehicles is resulting in a significantly rising number of controllers. This increasingly requires the use of smaller and lighter and also less expensive controllers. Such controllers could therefore also be used in mid-range vehicles or in small cars or for motorized bicycles in future.
To date, controllers have had a circuit module which comprises a circuit carrier, for example a printed circuit board or a ceramic substrate, electrical/electronic components and a package. The ever further rising demands with regard to robustness, such as corrosion resistance and temperature resistance, require new embodiments of the circuit modules. Thus, the package of the circuit module is increasingly in the form of a protective mass which surrounds the circuit carrier and the components. When the protective mass is produced, the circuit carrier and the components are usually encapsulated with a hard encapsulation material or surrounded with a thermosetting plastic by injection molding, for example by thermal transfer molding.
By way of example, laid-open specification DE 102 52 755 A1 describes a circuit module which comprises a circuit carrier, a circuit mounted on a circuit carrier and a discrete component, wherein the circuit is surrounded by a protective mass. In order to protect the discrete component from the strain during production of the protective mass, said discrete component has a protective shell which surrounds the discrete component. The protective mass covers both the circuit and the discrete component surrounded by the protective shell.
In this embodiment, however, it is not possible to use certain components, such as electrolytic capacitors or pressure sensors, on the circuit carrier, since these components cannot be embedded completely into the protective mass. By way of example, electrolytic capacitors do not withstand the pressure produced during encapsulation or injection molding in mechanical terms. It is also impossible to encapsulate electrolytic capacitors completely, since an electrolytic capacitor “breathes” during operation, i.e. the diameter of the electrolytic capacitor alters slightly during operation. By way of example, pressure sensors record the ambient air pressure which is usually required in controllers in vehicle engines for matching the injection molding parameters to the respective ambient air pressure.